﻿#region Copyright information
// 
// Copyright © 2005-2013 Yongkee Cho. All rights reserved.
// 
// This code is a part of the Biological Object Library and governed under the terms of the
// GNU Lesser General  Public License (LGPL) version 2.1 which accompanies this distribution.
// For more information on the LGPL, please visit http://bol.codeplex.com/license.
// 
// - Filename: ShannonEntropy.cs
// - Author: Yongkee Cho
// - Email: yongkeecho@gmail.com
// - Date Created: 2012-09-06 11:39 AM
// - Last Modified: 2013-01-25 3:59 PM
// 
#endregion
using System;
using System.Collections.Generic;
using System.Linq;
using BOL.Maths.Distributions;

namespace BOL.Linq.Probability
{
    public static partial class Probability
    {
        public static double ShannonEntropy<TKey>(this IDictionary<TKey, double> source)
        {
            return -source.Select(p => p.Value*Math.Log(p.Value, 2)).Sum();
        }

        public static double ShannonEntropy<TKey>(this INomialDistribution<TKey> source)
        {
            return source.ProbabilityTable.ShannonEntropy();
        }
    }
}
